arXiv subjects

Yuriy I. Kuzmin

Publications and source records attributed to Yuriy I. Kuzmin.

15 recordsLinked to original sources

arXiv2015

Ultimate Informational Capacity of a Volume Photosensitive Media

The ultimate information capacity of a three-dimensional hologram for the case of an optimal use of the dynamic range of a storage medium, number of pages, the readout conditions is considered. The volume hologram is regarded as an object of the information theory. For the first time the formalism of the reciprocal lattice has been introduced in order to estimate the informational properties of the hologram. The diffraction-limited holographic recording is analyzed in the framework of the reciprocal lattice formalism. Calculations of the information capacity of a three-dimensional hologram involve analysis of a set of multiplexed holograms, each of which has a finite signal-to-noise ratio determined by the dynamic range of the holographic medium and the geometry of recording and readout. An optimal number of pages that provides a maxi-mum information capacity at angular multiplexing is estimated.

cond-mat.mtrl-sci↗

arXiv2008

Vortex Dynamics in Percolative Superconductors Containing Fractal Clusters of a Normal Phase

The effect of fractal clusters on magnetic and transport properties of percolative superconductors is studied. The superconductor contains percolative superconducting cluster carrying a transport current and clusters of a normal phase. It is found that normal phase clusters have essential fractal features. The fractal dimension of the boundary of normal phase clusters is estimated. The current-voltage characteristics of superconductors containing fractal clusters are obtained. It is found that the fractality of the cluster boundary intensifies pinning. This feature permits to enhance the current-carrying capability of the superconductors.

cond-mat.supr-con↗

arXiv2007

Vortex Dynamics at the Initial Stage of Resistive Transition in Superconductors with Fractal Cluster Structure

The effect of fractal normal-phase clusters on vortex dynamics in a percolative superconductor is considered. The superconductor contains percolative superconducting cluster carrying a transport current and clusters of a normal phase, acting as pinning centers. A prototype of such a structure is YBCO film, containing clusters of columnar defects, as well as the BSCCO/Ag sheathed tape, which is of practical interest for wire fabrication. Transition of the superconductor into a resistive state corresponds to the percolation transition from a pinned vortex state to a resistive state when the vortices are free to move. The dependencies of the free vortex density on the fractal dimension of the cluster boundary as well as the resistance on the transport current are obtained. It is revealed that a mixed state of the vortex glass type is realized in the superconducting system involved. The current-voltage characteristics of superconductors containing fractal clusters are obtained and their features are studied.

cond-mat.supr-con↗

arXiv2007

Dynamics of the Magnetic Flux Trapped in Fractal Clusters of a Normal Phase in Percolative Superconductors

The effect of the fractal clusters of a normal phase, which act as pinning centers, on the dynamics of magnetic flux in percolative type-II superconductor is considered. The main features of these clusters are studied in detail: the cluster statistics is analyzed; the fractal dimension of their boundary is estimated; the distribution of critical currents is obtained, and its peculiarities are explored. It is found that there is the range of fractal dimension where this distribution has anomalous statistical properties, specifically, its dispersion becomes infinite. It is examined how the finite resolution capacity of the cluster geometric size measurement affects the estimated value of fractal dimension. The effect of fractal properties of the normal phase clusters on the electric field arisen from magnetic flux motion is investigated for the cluster area distribution of different kinds. The voltage-current characteristics of fractal superconducting structures in the resistive state are obtained for an arbitrary fractal dimension. It is revealed that the fractality of the boundaries of the normal phase clusters intensifies the magnetic flux trapping and thereby raises the critical current of a superconductor.

cond-mat.supr-con↗

arXiv2004

Initial dissipation and current-voltage characteristics of superconductors containing fractal clusters of a normal phase

The influence of fractal clusters of a normal phase on distinctive features of current-voltage characteristic of percolative type-II superconductors is considered. The results of high-resolution measurements of the differential resistance of BPSCCO/Ag composites are discussed in the context of magnetic flux dynamics. The region of initial dissipation is observed on current-voltage characteristics in the neighborhood of the transition into a resistive state. In the course of this stage of resistive transition the vortices start to break away from the normal-phase clusters, which act as pinning centers. The effect of transport current on vortex depinning is investigated. A broad current range of initial dissipation is considered as an evidence of fractal nature of the normal-phase clusters.

cond-mat.supr-con↗

arXiv2004

Peculiarities of the resistive transition in fractal superconducting structures

The influence of fractal clusters of a normal phase on the current-voltage characteristics of a percolation superconductor in the region of a resistive transition has been studied. The clusters represent the aggregates of columnar defects, which give rise to a correlated microscopic disorder in the system. Dependencies of the static and dynamic resistance on the transport current are obtained for an arbitrary fractal dimension of the cluster boundaries. It is revealed that a mixed state of the vortex glass type is realized in the superconducting system involved.

cond-mat.supr-con↗

arXiv2004

Depinning at the initial stage of the resistive transition in superconductors with a fractal cluster structure

Depinning of vortices in percolative superconductor containing fractal clusters of a normal phase is considered. Transition of the superconductor into a resistive state corresponds to the percolation transition from a pinned vortex state to a resistive state when the vortices are free to move. The motion of the magnetic flux transferred by these vortices gives rise to the region of initial dissipation on current-voltage characteristic. The influence of normal phase clusters on distinctive features of current-voltage characteristics of percolative type-II superconductors is considered. It is found that an increase in the fractal dimension of the normal phase clusters causes the initial dissipation region to broaden out. The reason of this effect is an increase in the density of free vortices broken away from the pinning centers by the Lorentz force. Dependencies of the free vortex density on the fractal dimension of the normal phase cluster boundaries are obtained.

cond-mat.supr-con↗

arXiv2003

Giant dispersion of critical currents in superconductor with fractal clusters of a normal phase

The influence of fractal clusters of a normal phase on the dynamics of a magnetic flux trapped in a percolative superconductor is considered. The critical current distribution and the current-voltage characteristics of fractal superconducting structures in the resistive state are obtained for an arbitrary fractal dimension of the cluster boundaries. The range of fractal dimensions, where the dispersion of critical currents becomes infinite, is found. It is revealed that the fractality of clusters depresses of the electric field caused by the magnetic flux motion thus increasing the critical current value. It is expected that the maximum current-carrying capability of a superconductor can be achieved in the region of giant dispersion of critical currents.

cond-mat.supr-con↗

arXiv2003

Pinning enhancement upon the magnetic flux trapping in the clusters of a normal phase with fractal boundaries

The magnetic flux trapping in type-II superconductor containing fractal clusters of a normal phase, which act as pinning centers, is considered. The critical current distribution for an arbitrary fractal dimension of the boundaries of the normal phase clusters is obtained. It is revealed that the fractality of the cluster boundaries intensifies the pinning and thereby raises the critical current of a superconductor. The pinning gain coefficient as a function of critical current for different fractal dimensions is calculated.

cond-mat.supr-con↗

arXiv2003

Anomalous statistical properties of the critical current distribution in superconductor containing fractal clusters of a normal phase

Statistical properties of the critical current distribution in superconductor with fractal clusters of a normal phase are considered. It is found that there is the range of fractal dimensions in which the variance and expectation for this distribution increases infinitely. Simple technique of avoiding such a divergence by the use of truncated distributions is proposed. It is suggested that the most current-carrying capability of a superconductor can be achieved by modifying the cluster area distribution in such a way that the regime of giant variance of critical currents will be realized.

cond-mat.supr-con↗

arXiv2002

Resistive state of superconducting structures with fractal clusters of a normal phase

The effect of morphologic factors on magnetic flux dynamics and critical currents in percolative superconducting structures is considered. The superconductor contains the fractal clusters of a normal phase, which act as pinning centers. The properties of these clusters are analyzed in the general case of gamma-distribution of their areas. The statistical characteristics of the normal phase clusters are studied, the critical current distribution is derived, and the dependencies of the main statistical parameters on the fractal dimension are found. The effect of fractal clusters of a normal phase on the electric field induced by the motion of the magnetic flux after the vortices have been broken away from pinning centers is considered. The voltage-current characteristics of fractal superconducting structures in a resistive state for an arbitrary fractal dimension are obtained. It is found that the fractality of the boundaries of normal phase clusters intensifies magnetic flux trapping and thereby increases the current-carrying capability of the superconductor.

cond-mat.supr-con↗

arXiv2001

Electric field induced by magnetic flux motion in superconductor containing fractal clusters of a normal phase

The influence of the fractal clusters of a normal phase, which act as pinning centers, on the dynamics of magnetic flux in percolative type-II superconductor is considered. The voltage-current characteristics of such a superconductor are obtained taking into account the effect of fractal properties of cluster boundaries on the magnetic flux trapping. It is revealed that the fractality reduces the electric field arising from magnetic flux motion and thereby raises the critical current of a superconductor.

cond-mat.supr-con↗

arXiv2001

Dynamics of the magnetic flux trapped in fractal clusters of normal phase in a superconductor

The influence of geometry and morphology of superconducting structure on critical currents and magnetic flux trapping in percolative type-II superconductor is considered. The superconductor contains the clusters of a normal phase, which act as pinning centers. It is found that such clusters have significant fractal properties. The main features of these clusters are studied in detail: the cluster statistics is analyzed; the fractal dimension of their boundary is estimated; the distribution of critical currents is obtained, and its peculiarities are explored. It is examined thoroughly how the finite resolution capacity of the cluster geometrical size measurement affects the estimated value of fractal dimension. The effect of fractal properties of the normal phase clusters on the electric field arising from magnetic flux motion is investigated in the case of an exponential distribution of cluster areas. The voltage-current characteristics of superconductors in the resistive state for an arbitrary fractal dimension are obtained. It is revealed that the fractality of the boundaries of the normal phase clusters intensifies the magnetic flux trapping and thereby raises the critical current of a superconductor.

cond-mat.supr-con↗

arXiv2001

Percolative shunting on electrified surface

The surface discharge of electrified dielectrics at high humidity is considered. The percolative nature of charge transport in electrets is established. Particular attention is given to the phenomena of adsorption and nucleation of electrically conducting phase in the cause of percolation cluster growth on electrified surface. The critical index of the correlation lenght for percolation cluster is found, and its value is in good agreement with the known theoretical estimations.

cond-mat.mtrl-sci↗

arXiv2001

Fractal geometry of normal phase clusters and magnetic flux trapping in high-Tc superconductors

The effect of geometry and morphology of superconducting structure on magnetic flux trapping is considered. It is found that the clusters of normal phase, which act as pinning centers, have significant fractal properties. The fractal dimension of the boundary of these clusters is estimated using a simple area-perimeter relation. A superconductor is treated as a percolation system. It is revealed that the fractality intensifies the magnetic flux trapping and thereby enhances the critical current value.

cond-mat.supr-con↗